tanaka_(chainsaw_man)
Mr. Tanaka a character from the manga series Chainsaw Man is a teacher of Mitaka Asa's class.
Mr. Tanaka is a kind man who values life and the well being of his students. He took special care to make sure Mitaka Asa felt included in the class, including asking the Class President (Chainsaw Man) to befriend her and apologizing to the class on her behalf for the death of Bucky (Chainsaw Man).
However, he may have been more unscrupulous then he seemed, as it was later revealed that he was sleeping with the Class President (Chainsaw Man) despite their age difference and student-teacher relationship.
After Yoru (Chainsaw Man) first arrives, she ripped off Mr. Tanaka's head, turning it into the "Tanaka Spinal Cord Sword". Most of his appearance in fanart is of the sword.